A. POLYMER HYDROGELS
Project A1: Biodegradable Polymer Hydrogels
Hydroyethyl methacrylate (HEMA) and related polymers
in the presence of water form hydrogels, which have been used for
medical applications, such as the manufacture of synthetic intra ocular
lenses, contact lenses, medical patches for burns treatment and the
preparation of controlled release formulations for pharmaceuticals.
A major aim in biomaterial science is to develop a material with the
biocompatibility of polyHEMA which degrades slowly in the human body,
thus providing an ideal scaffold for tissue regeneration. In this
project, to be conducted in collaboration with Prof. Traian Chirila
of the Queensland Eye Institute, new polymers will be prepared and
their response to the biological environment measured systematically.
Responsible Scientists Andrew Whittaker and Traian Chirila. Email:
Andrew Whittaker
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MRI Image of PHEMA Hydrogel |
Project A2: Hydrogels as Substitutes for Vitreous
Humour
The vitreous humour of the eye, the gel-like material
filling the bulk of the eye, may be lost through trauma to or disease
of the eye. This project, to be conducted in collaboration with Prof.
Traian Chirila of the Queensland Eye Institute, involves the development
of injectable polymeric replacements for the natural vitreous humour.
The project will involve synthesis of very high water content hydrogels
based on NVP and their combination with the natural components of
the vitreous humour (collagen and hyaluronic acid) in the form of
an IPN-type system. The project will involve studies of the chemistry,
stability, morphology and viscoelastic properties of the artificial
vitreous humour. Responsible Scientists Andrew Whittaker and Traian
Chirila. Email: Andrew Whittaker
Project A3: Novel Tri-Block Co-Polymers for Controlled
Release of Proteins for Osteogenesis
The aim of this project is to produce a biodegradable
controlled drug / protein release material for tissue engineering
applications. Gene sequences, angiogenic and osteogenic factors are
finding regular application in the clinical setting, however their
efficacy is highly dependant on the correct dose that is delivered.
Most delivery systems, particularly those based on hydrogels, rely
on Fickian diffusion, which doesn’t mimic the profile required
by the body to initiate wound healing. Non-hydrogel delivery systems,
such as PLGA microspheres, require the growth factors to be loaded
from an organic solvent which inherently denature the protein. The
basis of this project is to synthesise a triblock copolymer, that
is predominantly a hydrogel-like material, with interlinking hydrophobic
groups that can encapsulate and release the growth factor. The hydrophilic
region enables aqueous growth factor loading is also important for
controlling degradation rate, swelling, growth factor loading and
biological response. The hydrophobic segments encapsulate the protein
and enable release profiles that follow the degradation rate instead
of the diffusion rate. This project will involve polymer synthesis
and characterisation using IR, NMR, SEM and mechanical testing. Responsible
Scientist Idriss Blakey. Email: Idriss
Blakey
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Cover illustration from Advanced Functional Materials, 15,
2005. |
B. LIVING POLYMERS
Polymers made by living radical polymerization have
well-defined chain length and architecture. The structures that can
be synthesised are block, star, branched, gradient and even dendrimer.
The advantage of such a technique is the wide range of functional
monomers that can be incorporated in these architectures, allowing
materials from coatings to electronic devices to biomedical applications
to be prepared.
Project B1: Nanopolymer Composites
with Complex Architectures prepared in Water
The aim of this project is to synthesis
polymers with complex architectures (as shown above) on the nanoscale
in an environmentally friendly medium, water. The synthesis will involve
using a wide range of Living radical polymerizations towards a deeper
mechanistic understanding of the reaction pathways. Once these well-defined
nanostructures have been made their structure-property relationship
will be evaluated using structural characterization techniques such
as electron microscopy for size and morphology, and mechanical properties
using stress-strain and DMTA. These novel nanostructures will also
be functionalised for use as drug and gene delivery devices- this
is in collaboration with Prof. Istvan Toth. Email: Michael
Monteiro
Project B2: Mechanisms in Living Radical
Polymerization
Understanding the mechanisms in living
radical polymerization allows for better design of the living agents
and the optimal use of living polymerizations. The project will involve
the determination of the initiation mechanisms involved in Atom Radical
Transfer and Reversible Addition-Fragmentation chain Transfer polymerizations.
This will enable us to determine the dominant mechanisms and what
factors control addition, fragmentation and transfer reactions for
these living processes. Email: Michael
Monteiro
Project B3: New Materials for the
Removal of Nanomolar Levels of Heavy Metal Pollutants
We are developing polymeric materials
for application in the selective chelation and removal of heavy metal
ions (lead(II), mercury(II), cadmium(II)) present at extremely low
concentrations (<micromolar) in aqueous solutions. These heavy
metal ions, when absorbed in the body, either through inhalation,
through the skin, or ingestion usually react with sulfhydryl groups
in proteins and in large doses may denature and/or inactivate proteins
and enzymes and cause severe disruption to tissue. Major responses,
particularly to mercury, involve neurological and renal disturbances.
The maximum acceptable concentrations of mercury, lead and cadmium
in drinking water are 0.001 mg L-1, 0.05 mg L-1, and 0.005 mg L-1,
respectively. In water treatment most of the heavy metals, particularly
mercury, can be removed by ion exchange resins. Our interest is in
the lower levels of heavy metal ion contamination and the development
of materials which will remove these low levels.
Our approach is to use membrane filters
substituted with, in the first instance, polymeric ligands capable
of complexing with the mercury(II), lead(II) and cadmium(II). The
polymeric materials are prepared using RAFT (Reversible Addition Chain
Fragmentation) polymerization and then functionalized with the ligands.
The materials will be characterized using analytical methods such
as GPC, XPS, and electron microscopy. The uptake of metal ions will
be studied using appropriate isotopes of mercury, lead and cadmium
at the Materials and Engineering Science Division at ANSTO in Sydney.
Our ultimate goal is to incorporate into
the polymeric materials some of the compounds found in nature and
used by organisms to selectively chelate and remove toxic metal ions.
This project is in collaboration with Assoc Prof. Lawrie Gahan and
Dr. Michael Whittaker. Email: Michael
Monteiro
Project B4: Biomimetic Surface Construction
via Surface Confined ATRP and RAFT Processes From Isoporous Membranes
It has been demonstrated that when these
architecturally complex molecules are cast under certain conditions
they will spontaneously form isoporous inverse opal substrates and
honeycomb structured films, as shown below. The pore size and film
functionality are easily controlled through the judicious choice of
functional monomer, casting conditions and molecular weight. These
isoporous films possess considerable potential for biomedical and
biotechnological applications due to their high surface area, predetermined
pore size and controlled surface functionality. Possible applications
are as biosensors, cells and tissue scaffolding and as high surface
area supports for oligonucleotide/protein arrays. This project will
involve the synthesis of architecturally complex molecules by ATRP
and RAFT chemistries. These will be characterized by NMR and GPC.
Films will be cast from these materials and characterized by optical
microscopy and scanning electron microscopy. The surface chemistries
of the films will then be modified as described above and further
characterized by x-ray photoelectron spectroscopy and attenuated total
reflectance FTIR. The use of these modified films in array formats
will be explored. This project is in collaboration with Dr. Michael
Whittaker. Email: Michael Monteiro
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Styrene-based film with a 1 um pore size |
C. POLYMERS FOR TISSUE ENGINEERING
Project C1: Synthesis of Glass-ionomer Cement (Polymers)
for Dental Applications
Current glass-ionomer cements (GIC) have a number
of properties which make them highly suitable as materials for the
restoration of teeth, a cementing agent for the attachment of crowns
and bridges, a cavity liner and as a general repair material. GICs
form a hard material upon setting; they exhibit no exothermic reaction
and no shrinking during setting; they have high dimensional stability
and good adhesion to tooth structure, due to a strong ionic bond to
the calcium ions on the surface of enamel or dentin (good biocompatibility
and they release fluoride ions to protect against decalcification).
The commercial GIC cements which are currently used for dental restoration
experience inherent problems that are associated mainly with their
chemical compositions, which results in poor interaction with glass
powder (poor ionic bonds due to steric hindrance). The objective of
research in this area is to investigate a range of alternative monomer
systems which form copolymers with the traditional GIC monomers (poly
acrylic acids), with the aim to improve GIC mechanical and chemical
performance as dental materials. Responsible Scientist Firas Rasoul.
Email: Firas Rasoul
Project C2: Bio-degradable Polymers for Tissue
Engineering Scaffolds
Tissue engineering has come to mean the regeneration
of a tissue type either in the laboratory or in the patient. Successful
tissue regeneration requires an interplay between three components:
the cells that create the tissue, a scaffold or matrix to hold the
cells and create the tissue’s physical form, and biological
signaling molecules that direct the cells to form the desired tissue
type. Designing the matrix or scaffold is often the most daunting
task in any tissue engineering project. The overall objective of the
program is to develop novel polymer scaffolds for repairing dental
implant and treating dental defects (like poor bonding between teeth
and under-lying jawbone). This project aims to investigate the synthesis
and characterisation of novel polymer system based on the newly developed
Click-Chemistry approach, which will then be used for scaffold assembly.
A small library of polymers based on different molecular weight polyethylene
glycols (PEGs) functionalised with acetylene end groups crosslinked
with tri and tetra-functionalised azide moieties. The water absorption
capabilities of the crosslinked polymers will be characterised by
NMR. Structural characterisation will be conducted by using several
spectroscopic techniques such as FTIR, XPS and others. The degradation
rates will also be studied using simulated body fluid media. Responsible
Scientists Firas Rasoul and Andrew Whittaker. Email: Firas
Rasoul
| Polymer scaffold foamed using supercritical -CO2 |
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Project C3: Bio-polymer Beads for Drug Delivery
This project aims at synthesis and characterisation
of biopolymers (a flexible polymeric template) specifically targeting
the delivery of drugs with poor bioavailability. This polymeric template
will be made from a water soluble hyper-branched nano beads having
several reactive sites that can be functionalised with different polymeric
chains. The objective of this project is to use combination of polymerisation
techniques (for example ATRP and the newly developed Click-Chemistry)
to initiate polymerisation with controlled architecture and hydrophilicity.
These newly developed nono-beads with unique features can be used
for delivering multi-drug systems. Project in this area would involve
polymer synthesis and characterisation using techniques such as FT-IR,
NMR and GPC. The developed polymer will be tested for drug delivery.
Responsible Scientist Firas Rasoul. Email: Firas
Rasoul
Project C4: Surface Grafting of Bio-Compatible
Polymers
Although many bulk commodity plastics are relatively
cheap and have good mechanical properties, often they perform poorly
when placed in contact with biological media. For example, proteins
will denature on the surface of many commodity plastics, which is
often undesirable. Recently, we have developed a number of methods
for the modification of commodity plastics such as polyolefins and
fluoropolymers. The objective of this project is to modify the surface
of commodity plastics using these techniques to generate bio-compatible
surfaces, which will find applications such as, membranes for protein
separation or non-adsorbing surfaces for protein and other biomolecules
packaging. The project would involve preparation of grafted surfaces
using a variety of conditions such as radiation grafting and surface
re-initiation. Several analytical and spectroscopic techniques will
be used to characterise and evaluate the grafted surfaces including
XPS, FTIR, SEM and protein adhesion assays. Responsible Scientists
Idriss Blakey, Firas Rasoul and Andrew Whittaker. Email: Idriss
Blakey
Project C5: Studies of the Degradation Rates of
Biodegradable Polymers
A rapidly-developing field of materials science is
that of biodegradable polymers. These materials are formed into various
shapes and placed in the human body as supports for soft or hard tissue
regeneration. Recently chemists have been aiming to expand the number
of materials available to the end user, the surgeon or dentist. It
is critically important that an understanding of how these polymers
degrade within the body is established. In this project the fundamental
rates of degradation of model compounds of the biopolymers will be
studied in-vitro, using advanced NMR facilities. Following this a
predictive model will be developed relating the material structure
and fundamental degradation rate. This will be coupled with a transport
model to allow a complete description of the degradation processes.
Responsible Scientist Andrew Whittaker. Email: Andrew
Whittaker
| Surface versus Bulk Degradation.
The dominant mechanism of degradation is determined by the
relative rates of diffusion and degradation. |
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D. POLYMER DEVICES
Project D1: Properties of Grafted Fluoropolymer
Membranes
Recently we have developed a method of producing radiation-grafted
fluoropolymer films with potential application as proton exchange
membranes. These membranes could be used in fuel cells. Although the
materials have been well characterised, we have not developed their
potential as exchange membranes, or determined how changes in the
grafting conditions will affect transport and exchange rates of the
membranes, important properties for any potential material. The project
would involve preparation of grafted films under a variety of conditions
and measuring transport and ion exchange capacities. Collaboration
with Dupont Central Research of Wilmington is being negotiated. Responsible
Scientist Andrew Whittaker, Firas Rasoul and Idriss Blakey. Email:
Andrew Whittaker
| Raman map of grafted fluorpolymer
surface |
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Project D2: Generation of Functional Polymer Surfaces
for Use as Catalyst Supports
Metal based catalysts play an important role in many
organic reactions. However, often it can be problematic to remove
the catalyst from the final product, especially in a form that it
can be reused. For example, chemicals and polymers used in the microelectronics
industry need to be extremely pure and free from metal contamination
in particular. A method to overcome metal contamination of reaction
products is to use polymer supported catalysts. This project will
involve generation of functional polymer surfaces that can be utilised
as supports for metal catalysts. This will involve the radiation grating
of functional monomers to an inert polymer substrate and then attachment
of the metal centers and cocatalysts. A range of techniques will be
utilised to characterise these systems such as XPS, solid state NMR,
FTIR and Raman microscopy. The final stage of this project will be
to test the efficacy of these supports in model reactions. Responsible
Scientist Idriss Blakey. Email: Idriss
Blakey
Project D3: Laser Ablation of Materials Surfaces
for Cell Attachment
The attachment of cells to polymer surfaces is of
crucial importance for a wide number of applications, for example
tissue engineering, implant stability and drug delivery. A number
of polymers have been shown to demonstrate improved cell attachment
after irradiation with high energy lasers. The laser irradiation leads
to ablation and to alteration of the chemical structure of the polymer
surface. It is possible to moderate the effects of the laser light
by irradiation in the presence of gaseous additives. In this project,
to be conducted in collaboration with Prof. Traian Chirila of the
Queensland Eye Institute, we will investigate the laser modification
and cell attachment of the important biomaterial polyHEMA. The project
will involve elements of modern characterisation (AFM, XPS, SEM, NMR
etc.), surface chemistry, and cell-material science. This project
lies at the interface of the physical and biological sciences. Responsible
Scientists Andrew Whittaker and Traian Chirila. Email: Andrew
Whittaker
Project D4: New Resist Materials for Nanoimprint
Lithography
Nanoimprint lithography is one of the most promising
technologies for mass production of devices with nano-sized patterns,
and is regarded as a key tool for the next generation lithography.
The technology has demonstrated 10 nm feature sizes, 40 nm pitch,
vertical and smooth side-walls, and nearly 90 degree corners. Recent
studies have indicated that the ultimate resolution of nanoimprint
lithography could be sub-10 nm. However, currently-used resists have
disadvantages in various aspects such as viscosity, mechanical properties,
plasma etching behaviour, etc. It is the aim of this project to develop
a suitable UV-curable resist for this new process. Techniques required
in this project are monomer and polymer synthesis and characterisation
including NMR, FTIR, GPC, DSC, DMA etc. Responsible Scientist Heping
Liu. Email: Andrew Whittaker
Project D5: New Substrate Materials for Printed
Circuit Boards with Low Dielectric Properties
Global demand for electronic products and the printed
circuit boards used to make them continues to rise. Rapid technological
advances have permitted the incorporation of more and more functions
onto ever-smaller printed circuit boards. In addition, improvements
in integrated circuit processing have dramatically increased circuit
speeds. One of the requirements for the substrate is low dielectric
constant and dissipation factor. It is the aim of this project to
satisfy these requirements using quantitative structure property relationships
(QSPR) as a guide. Dielectric properties for simple molecules can
be easily found in the literature. Using this data, a QSPR model can
be established which in turn can be used to predict the dielectric
properties of a new material. From this process, a large pool of candidates
can be screened and only a small group, which satisfies the desired
properties, will be synthesised and evaluated. Techniques required
in this project are computer modelling, monomer and polymer synthesis
and characterisation including NMR, FTIR, GPC, DSC, DMA etc. Responsible
Scientist Heping Liu. Email: Andrew
Whittaker
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Exposed and developed polymer resist film |